Championship Kalista is the Season V Skin for this year World Championship.
During Patch 5.18, Championship Kalista Skin will be released, joining the existing Championship Skins Gallery, such as Riven, Thresh and Shyvanna. The Price is 975 RP.
Championship Thresh (Season III)
Championship Shyvana (Season IV)
Championship Kalista (Season V)
This is one of the features of the Patch 5.18 for the World Championship, like the new Ward Skin, Summoners Icon and Emblems.
All this information was taken from PBE server.